The average native speaker of any language uses around a tenth of his vocabulary in everyday speech. In other words, around 1200 to 2000. Link: http://englishenglish.com/english_facts_13.htm 1) How many words do we need to know? It depends on what you want to do with the language. If the goal is to travel abroad, the most frequent 1000 words are probably enough. If you want to become fluent you will need a lot of words. The frequency of words declines quickly after the first 500 or even 1,000. In English (and many other languages), the most frequent 1,000 words may account for 70% of the content of a conversation , but the next 1,000 add only 3-5% , and after that there is not much difference in the utility of words regardless of where they place in the frequency lists. If the goal is to communicate comfortably, read, and become fluent in the language, I believe 5,000 word families, or 8,000 words is a realistic first goal. In any case we recommend learning a lot of words....